Some filters for electronics enclosures incorporate filter materials that can shed particulate material into the enclosure environment, which can be undesirable. The filters typically incorporate multiple layers of filter material that are welded together adjacent their outer perimeters. Attempts have been made to rectify the shedding issue by adding outer layers that are configured to contain the shed particulates within the filter assembly. In such attempts, the outer layers are layered against the outside surfaces of the filter material. The outer layers are generally coextensive with the outside surfaces of the filter material. The outer layers and the layers of filter material are then welded together in a weld area that is at, or adjacent to, the outer perimeter of the filter.
FIG. 6 depicts an example recirculation filter 500 known in the art. The recirculation filter has outer scrim layers 510, 520 that contain a filter material layer 530. The outer scrim layers 510, 520 are welded to each other and the filter material layer 530 in a perimeter region 550 of the filter element 500.
It has been discovered that friction and other forces acting on the filter element 500 can partially dislodge and shift the ends of individual fibers 532 of the filter material layer 530 to protrude from the filter material layer 530 and extend beyond the outer layers 510, 520 of the filter element 500 that are configured to contain such fibers. Such forces can result from manufacturing the recirculation filter, from shipping the recirculation filter, and from handling the recirculation filter such as during manufacturing of an electronics enclosure—when the recirculation filter is being installed or inserted into the recirculation filter holder contained in the electronics enclosure—and during operation of the electronics enclosure, when the recirculation filter is in use. For example, the outer layers of the recirculation filter can rub against the filter material fibers, which can result in unwanted filter fibers shifting and extending into the electronics enclosure.